Optical fiber link and CATV RF test device

Innovative field test device for every optical fiber technician

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This is the upgraded version of my #Fiber optic Power/Link tester, but this version in designed as part of my university bachelor degree work. So general description will be here.

The range of modern optical fiber measuring equipment is quite wide, however, often had to
operate with, at the same time, several measuring equipment and still impossible to perform out,
periodically, specific measurements. When there is a need for portable, easy-to-carry and in-use
in-field test equipment in directions such as CATV RF signal detection in optical fiber, or
transmitter wavelength and connection speed identification, there are only oversize solutions that require external power supply and combine multiple equipment at once to obtain the desired result.
The purpose of the result is to create a prototype for a test device that will be able to identify the working wavelength, measure optical signal power, determine connection (link) speed, identify the presence of CATV RF signal.

Before all are safety! - Laser safety

What this device is for? 

This is in-field test device which can test & measure:

  1. Identify working wavelength;
  2. Measure optical power;
  3. Determine the connection link speed;
  4. Identify the existence of a CATV RF signal;
  5. Works as calibrated laser source.
  • Technical parametrs:
    • Working wavelength: 800 ~ 1700nm;
    • Optical power range: -50dBm ~ +26dBm;
    • Calibrated wavelength: 850/1310/1490/1550/1650nm;
    • Calibrated laser source: 1310/1490/1550nm
    • Laser source modulation: CW (continuous wave), 270/330/1k/2kHz;
    • Laser source power: -7 ~ 0dBm;
    • Resolution: 0,01dB;
    • ID frequency: 270/330/1k/2kHz;
    • Operational temperature: -25 ~ +60ºC
  • PON test device technical parametrs:
    • Filter wavelength: 1310/1490/1550nm;
    • Channel isolation: >40dB;
    • Passthrough IL: <7dB.
  • RF signal detector:
    • RF detection: 10 ~ 1000MHz;
    • Attenuation range: 0 ~ 31.5dB;
    • Attenuation step: 0.5dB.
  • Connection speed determiner:
    • determiner link speed: 100/1000Mbp/s;
    • Working wavelength (Tx/Rx): 1310/1550, 1550/1310, 1490/1310nm.

test link (if other side connected to SFP or media converter (MC)) 100/1000Mbps for one or two fibers link,

  • How does it works? 

This test device have 2 optical ports. First port is for standart using, then we need to determine: working wavelength, optical power, identify the existence of a CATV RF signal, and link connection speed. Second optical port needed if we will measure PON (passive optical network). ;

But now about everything in details...

First Optical port for optical power, wavelength and link tester

Connected optical power goes through two opto-mechanical switch (next OMswitch) to the first Sp1 PLC splitter (Planar Lightwave Circuit) 1/2 with 50/50% insertion loss (what is approximately ≤4.0dB) with one output directly to the first photodiode D1 for optical power measuring.

Second output of the first splitter connected to Sp2, which needed for making "passthrough" channel for PON testing, to the Sp3 - which collects two line signals to one output (this splitter also needed also needed due to PON network measurements). After all optical line connects to the first FM1 FWDM (Filter Wavelength Division Multiplexer)Pass line of this filter with filtered 1490nm connected to the second photodiode D2 for optical power detection/measurement of 1490nm, Reflected line with filtered 1310 and 1550nm connected to the second FM2 filter. Second filter Pass and Reflected lines connected to photodiodes D3 and D4 for 1550nm and 1310nm optical power detection/measurement respectively.

Each photodiode is InGaAs photodiode. 

Because each photodiodes requires an operational amplifier with a programmable gain factor (since the power range is too wide 76dB), a solution was found using only one programmable operation amplifier for all four photodiodes. But I'll describe this step a little later.

So when microcontroller detects signal from one of photodiodes and if this signal will not be higher as -2dBm, microcontroller will switch OMswitch to defined SFP 1310, 1550 or 1490nm (if detected signal will be from 1550nm photodiode - will be switched to 1550 SFP, if detected from 1310nm - will be switched first to the 1310 and so on).

Next step is detecting link speed (if other side connected to SFP or to MC-media converter). This stage are realized through integrated into SFP DDM (Digital Diagnostic Monitoring). DDM can show us not only transceiver temperature, supply voltage, laser bias current, transmitted average optical power, received optical modulation amplitude (OMA) or Average Optical Power, but also by received code detect link speed and identify SFP or MC connected at the other end of the fiber.

Second port for PON testing

Optional* - Third port, visual laser source

Very often need to determinate/identify correct fiber port...

Read more »

Adobe Portable Document Format - 748.28 kB - 04/29/2019 at 21:16


Adobe Portable Document Format - 812.38 kB - 04/29/2019 at 21:16



Test device schematic

Adobe Portable Document Format - 297.70 kB - 04/29/2019 at 21:15


AiO Power meter ENG.pdf

Optical fiber link and CATV RF test device block diagram

Adobe Portable Document Format - 60.42 kB - 04/29/2019 at 21:15


  • Working on the project will begin

    Aleksejs06/21/2019 at 09:39 0 comments

    My work on this project is not fished. 

    I spent all-time for my degree work writing and a little bit project software part debugging. 

    But for now I officially have graduation as elektronical engeneer! YEAH I DID IT!!! 

    Now I have more time to spend for my projects! 

    And of course don't forget to comment ideas, work and options what is more or less needed. 

  • Optical fiber cabel installation

    Aleksejs05/31/2019 at 16:48 0 comments

    As I'm at the telecommunication operator fiber optic technician I finally installed and fused to my apartments optical fiber cabel from outside ODF (optical distribution frame) with CATV analog and digital signals. 

    So the next step is to start testing/debugging and coding RF digital attenuator with RF Log detector. 

    But for now I must finish my bachelor degree paper works and print out the book for my graduation. 

  • OpAmp MUX testing

    Aleksejs05/23/2019 at 23:03 0 comments

    Here is some testing report video of my automatically OpAmp gain switching depending on recieved laser signal with InGaAs photodiode. 

    Led switching indicate gain mux switching position. 

    On LCD display you can see sfp module TX power, InGaAs Photodiode RX power, sfp module temperature and voltage. And the last line indicate mux switching position number. 

    I2c driver little helped me with some different SFP modules:) 

  • Photodiode MUX testing... and little fail

    Aleksejs05/19/2019 at 22:07 0 comments

    I'll begin from a little fail with photodiode Mux.

    At beginning of my PCB testing input block - pdotodiode input MUX I realized what I forgot to add mux switching pins and Logic high (+2.5v) pins for mux controlling:( That's was my second fail and next board hacking for adding this additions.

    Added two pin headers for Mux logic control and three pin header for logic control - Logic High.

    Mux switching tested by manually input switching between four inputs with Logic control inputs pins.

  • SFP Testing

    Aleksejs05/19/2019 at 21:52 0 comments

    There are more SFP DDM libraries founded on the Internet for reading all necessary information from SFP modules.

    For now I get from SFP: TX bias current, TX power, RX power, module temperature, voltage, TX laser wavelength:

    On LCD display You can see:

    • SFP transceiver TX power values;
    • Photodiode RX power received from SFP module;
    • SFP module temperature;
    • SFP module voltage;
    • SFP module laser wavelength.

  • SFP connecting

    Aleksejs05/14/2019 at 07:10 0 comments

    After hacking my board (after i make mistake with footprint It's soldering time... Part 3. Final step.) I started testing and modifying software writed by @oakkar7 (GitHub link) for my needs.

    At firs time I get almost all needed information from SFP module.

    This are: TX and RX power, temperature, voltage, transceiver wavelength, active link status.

    On the right upper corner located 100Mbp/s media converter (D-link DMS-920R) with TX 1310nm/ RX 1550nm. It's connected to the SFP, located on my device board. SFP with TX 1550nm/ RX 1310nm.

    Display currently shows information readed from SFP DDM interface (on this photo I didn't indicate SFP module wavelength).

    LED (on the left side) indicate SFP receiver status.

  • It's soldering time... Part 3. Final step.

    Aleksejs05/13/2019 at 07:04 2 comments

    Looking back at my previous log (It's soldering time... Part 2. Step by step log.) You remember what I have some problem with wrong footprint? Yeahh :( 

    The solutions is my soldering skill testing :) But I just have some cheap chinese soldering iron with bold (2mm) tip. And part led pitch are 0.5mm. This is a real challenge to my skills.

    After hours of soldering finally I get this:

    Not so pretty as I would like, but there are no shorts and, I hope, it will work.

    Let's start testing ...

  • It's soldering time... Part 2. Step by step log.

    Aleksejs05/09/2019 at 11:20 0 comments

    As the beginning of my Step-by-step log I'll show in pictures how goes my manual :))) Pick&Place machine :))) 

    And what goes wrong :(

    In It's soldering time... my step by step log. Part 1. I finished with removing remaining solder paste on stencil...

    1. Now it's time to show what's after accurate removing stencil from pcb:

    As You can see everything looks pretty nice! All footpads and especially small footpads with pitch from 0.65 to 0.45! are great covered with solder paste. I'm really happy with my first fork with stencil.

    2. It's time to turn ON my "Pick&Place machine" :) - my eyes, hands and tweezers :)))

    Every minute the number of components increased...

    And more increased....

    And until this step my happiness was no limit, until..... I unpacked next components to pace them....

    Ouuuuu..... :((((

    This wasn't what I expecting. 

    I several times change my component at schematic, but forgot to change also footprint.


    Don't forget, as I did, to double check, but better double-double check used and ordered parts in the project.

    To be continued....

  • It's soldering time... my step by step log. Part 1.

    Aleksejs05/07/2019 at 09:09 0 comments

    This is first part of my soldering log.

    With starting of this project I also decide to try my first time soldering stencils (it is necessary to gain experience). As You saw before I already get my order with PCB's and stencil.

    For solder paste I ordered from Chip Quick "Thermally Stable Solder Paste No-Clean Sn63/Pb37 T4 (50g jar)" P/N:TS391AX50 with Revolutionary Formula: No Refrigeration Required! 

    Here preparing for soldering photo log with some comments:

    1. Unpacking stencil and preparing pcb:

    Stencil was packed two sides in hard board and the holes on both sides are sealed with a film so can't get there.

    2. I use same hard board and other pcb's for central board holding:

    This was same and my other project pcb's.

    3. Next is centring and fixing stencil:

    Stencil is placed and fixed. Get it correct only at second attempt. On the photo You can only see big alighting places, but trust my the smallest also are aligned :)

    4. Preparing and applying solder paste:

    Stencil fixed, solder paste ready for spread...

    5. Solder paste spreading:

    Paste spreading (I use some plastic card) from one side to other and back...

    6. Next need to clean out remaining paste:

    With same plastic card I clean put remaining solder paste...


    Working with stencil it's pretty simple steps, and where you need, depending on Your design component pitch and pin sizes, select right solder paste powder size and as hobbyist (my opinion) better select No-clean paste for fastest forking :)

    AND accurate align and fix stencil over the board, and after accurate removing stencil from the board.

    At my log Part 2 You'll see how goes my soldering, and what's was wrong with the plan :(

  • PCB design and orderign

    Aleksejs04/30/2019 at 16:10 0 comments

    After spent time on PCB design, where I tried to combine different device nodes at the same time using this PCB as prototype board. On it I can control and read any devices module separately. All output and control pins traced to connector headers for future operations.

    So the device board spitted by the blocks: 

    • Photodiode MUX,
    • OPamp witch two muxes for variable gain control,
    • RF variable attenuation with RF Log detector,
    • ADC,
    • Three ports for SFP modules.

    Of course for ease soldering with PCBs I order stencil :)

    Next step will be.... 

    Yes! Soldering :)

View all 14 project logs

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wendy wrote 04/11/2023 at 03:29 point

FTTH equipments can be obtained through

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Coin123 wrote 07/06/2021 at 06:54 point

Great article! Read with pleasure.

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wendy wrote 04/15/2023 at 01:45 point

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Dave's Dev Lab wrote 04/29/2019 at 21:24 point

awesome looking project and design! will you be posting the design files? if so, under what license?

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Aleksejs wrote 04/30/2019 at 09:17 point

Thanks! Yes, I'll post the design files, but now I'm thinking/reading about selecting correct license. 

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Aleksejs wrote 05/13/2019 at 15:46 point

Hi Dave, I'll post everything under GPL-3.0. There are still little bit wrong schematic, now I'm working on software side, but I'll try to update existing files soon. 

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Dave's Dev Lab wrote 05/13/2019 at 16:07 point

thanks for the update! i'll have a look!

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